Glass composition



2,972,544 GLASS COMPOSITION Chikara Hirayama,

house Electric Corporation, poration of Pennsylvania No Drawing. Filed Oct. 22, 1959, Ser. No. 847,911 '2 Claims. (Cl. 106-53) Murrysville, Pa., assignor to Westing- East Pittsburgh, Pa., a cor- States Patent Certain electrical properties of the four glass compositions set forth in Table I above were determined. Glass discs were prepared from each of the glass compositions set forth in Table I. The discs were prepared by casting molten glass of the desired composition in a suitable mold -.to produce a disc having a diameter of about 1.5 inches and a thickness of about inch. The discs were ground and polished to a thickness of about 2 millimeters. Each glass disc was provided with suitable electrodes for making the necessary electrical connections for conducting the tests by applying to both surfaces thereof a silver paint comprising finely divided silver particles dispersed in a resinous vehicle. 'Tests were performed to determine the specific resistance properties of the several glass compositions, the dissipation factor and the dielectric constant. These determinations are set forth in Table 11 below. Tests were conducted at the various temperatures indicated.

Table II Dissipation Factor, 100 Dielectric Constant Specific Resistance, Test tan a ohm-cm. Glass Composition 'Ignap,

60 cy. 1 key. 100 key 60 cy. 1 key. 100 key. 1 Min. 2 Min.

102 0. 22 0.13 0. 56 10. 9 10.8 10.9 1. 9X10" 4. X10" 205 0. 60 0.18 0. 43 11. 1 11. 1 11. 0 2. 0X10 2. 1X10 A 305 7. 30 1.19 0.48 11.7 11.4 11.3 7. 4X10 7.-4X10 404 162 16. 4 0. 86 16.0 12.1 11.4 1. 1X10 1. 1X10 500 186 5. 54 18. 7 12.2 6. 0X10 6. 2X10 102 0. 57 0. 13 0. 38 9. 8 9. 7 9. 8 3. 0X10" 1. 5X10" 205 0.50 0.16 0. 47 10.1 10.0 9. 9 1. 4X10 1. 4X10" B 305 3. 64 0. 63 0.49 10.4 10. 2 10. 2 3. 0X10 3. 0X10! 404 59. 90 6. 36 0. 47 12. 3 10. 6 10. 2 3. 9X10" 4. 0x10 500 83.2 2. 73 13.1 10.8 1. 7X10 1. 8X10 102 0.17 0. 11 0.32 10.2 10.1 10. 1 3. 4X10" 1. 1X10" 205 0. 27 0. 16 0. 33 10. 3 10.2 10.2 9. l X 9. 5X10 O 303 2. 51 0.56 Y 10.6 10.4 10.4 2. 3X10" 2. 3X10 402 71. 18 7. 85 0. 45 12. 8 11.0 10. 6 3. 8X10 3. 9X10 600 106 3.00 14. 0 11.0 1. 2X10 1. 2X10 102 0.28 0.14 0.40 9. l 9.0 8. 9 4. 0X10 2. 4X10" 205 0. 22 0. 12 0. 40 9. 2 9. 2 9. 0 9. 0X10 9. 9X10 D 303 1. 00 0. 35 0. 36 9. 5 9. 2 9. 2 1. 7X10 1. 6X10" 402 20. 66 2. 73 0.40 10.2 9. 6 9. 4 1. 6X10 1. 6Xl0 500 34. 7 1. 34 l0. 7 9. 6 6.1X10 5. 2X10 and 30% BaO, between 10% and 20% B 0 between 5% and 20% SiO between 4% and 10% CaO, and between l% and 10% A1 0 Any remaining ingredients in the glass composition will be in the form of impurities and will be restricted to below about 2%.

Preferred glass compositions fall within the following ranges of percentage composition by weight, viz: between 22% and 32% PhD, between 25% and BaO, between 12% and 20% B 0 between 8% and 19% SiO between 5% and 8% CaO, and between 4% and 9% A1 0 Four glass compositions, falling within the preferred ranges above given, are set forth in Table 1 below. The glass compositions are accompanied by their thermal expansion coefficients, sag points, and specific gravities.

For the purposes of this invention, sag point is defined I as that temperature at which a filament of the glass, 2 centimeters in length and 0.16 millimeter in cross sectional diameter, will begin to sag under its own weight when heated throughout its entire length.

The glass compositions of this invention have particular application as electrical insulating media for high temperature applications. Application of the glass of this invention will usually be made in finely divided form, preferably in admixture with a suitable finely divided electrical insulating refractory material such as silica (S102), alumina (A1 0 zirconium silicate (ZrSiO and the like.

To prepare finely divided particles of glass, ingredients in amounts necessary to provide the desired glass composition are placed in a suitable vessel, dry mixed and then heated to a temperature of from about 1000 C. to about 1100 C. at which temperature the ingredients fuse and form a homogeneous molten glass mass. The molten mass of glass is then poured into water and the glass is shattered (the resulting product being known as frit). This frit is ball-milled either wet or dry to the desired particle size.

The glass compositions of this invention in admixture with electrically insulating refractory materials are particularly suitable for electrical insulating coatings and Table l Sag Specific Expansion Glass PbO B20; A1203 BaO SiO, CaO Point, Gravity (25-450 0.)

encapsulants that will be satisfactory for use at temperatures up to about 500 C. It will be noted from the sag points set forth in Table I that electrical insulating coatings comprising the glass compositions of this invention will not be adversely affected by the softening of the glass atoperating temperatures as high as about 500 C. Furthermore, the glass compositions of this invention, in finely divided form, will fuse and coalesce when heated to temperatures of from about 700 C. to about 750 C.

and at these temperatures the glass has suflicient viscosity 10 20% to 35% PhD, from 10% to 20% B from 20% to 30% BaO, from to SiO from 4% to 10% CaO, and 1% to 10% A1 0 2. A glass composition consisting of, by weight, from 22% to 32% PhD, from to B210, from 12% to 20% B 0 from 8% to 19% SiO from 5% to 8% 0:10, and from 4% to 9% A1 0 References Cited in the file of this patent UNITED STATES PATENTS 2,393,450 Armistead Jan. 22, 1946 2,417,898 Armistead Mar. 25, 1947 15 2,431,983 Bastick et a1. Dec. 2, 1947 2,702,749 Hafner Feb. 22, 1955 

1. A GLASS COMPOSITION CONSISTING OF, BY WEIGHT, FROM 20% TO 35% PBO, FROM 10% TO 20% B2O3, FROM 20% TO 30% BAO, FROM 5% TO 20% SIO2, FROM 4% TO 10% CAO, AND 1% TO 10% AL2O3. 